JP2007234455A - Printer head, manufacturing method of printer head, and printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer head capable of improving printing quality by suppressing a blur of light emission of an organic EL element 3, and improving reliability by securing a light emission lifetime of the organic EL element 3. <P>SOLUTION: The printer head is provided with a light source array including a plurality of the organic EL elements 3 which are aligned and arranged and have a hole injection layer 70 and light emission layer 60 arranged on a surface of a positive electrode 23, and a lens array formed by arranging lens elements for imaging light from the light source array. The hole injection layer 70 contains a metal element same as that of a pixel electrode 23. A problem can be solved by enhancing electric resistance of the hole injection layer 70 by degrading a function of dopant existing in the hole injection layer 70 by positive ions of the metal element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printer head, a printer head manufacturing method, and a printer.

  A line printer (image forming apparatus) is known as an electrophotographic printer. In this line printer, devices such as a charger, a line-shaped printer head, a developing device, and a transfer device are arranged close to each other on the peripheral surface of a photosensitive drum serving as an exposed portion. That is, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum charged by the charger by selective light emission operation of a light emitting element provided in the printer head, and this latent image is developed. The toner image is developed with toner supplied from the container, and the toner image is transferred onto the paper by the transfer device.

  As the demand for higher printer printing speed and space saving increases, tandem printing methods are becoming mainstream in recent years. Therefore, a light emitting diode (LED) has attracted attention as a light emitting element of the printer head. Printer heads using LEDs have been demonstrated to exhibit high printing characteristics, but there are many problems to be overcome, such as brightness variations and manufacturing costs. In contrast, printer heads using organic EL elements (see, for example, Patent Documents 1 and 2) are excellent in luminance variations, manufacturing costs, and space saving, and have the ability to compete with LED heads.

An organic EL element is provided with an organic light emitting layer between an anode and a cathode. In this organic EL element, holes supplied from the anode and electrons supplied from the cathode are recombined in the light emitting layer to emit light. In order to improve the efficiency of hole injection from the anode to the light emitting layer, a hole injection layer is often formed between the anode and the light emitting layer.
Japanese Patent Laid-Open No. 7-22649 JP 2004-327217 A

Generally, high brightness is required for the light source of the printer head. Therefore, it is necessary to ensure a high luminance by applying a large current to the organic EL element. However, when a large current is applied to the organic EL element, there is a problem that light emission outside the pixel region (so-called light emission blur) occurs. It is considered that this bleeding of light occurs when the current supplied from the anode spreads in the plane direction of the hole injection layer. This blurring of light emission causes the print quality of the printer to deteriorate.
Further, when a large current is applied to the organic EL element, there is a problem that the light emission lifetime is reduced. The reliability of the printer head decreases due to the decrease in the light emission lifetime of the organic EL element.

  The present invention has been made to solve the above-mentioned problems, and can suppress the bleeding of the light emission of the organic EL element to improve the print quality and ensure the light emission life of the organic EL element. It is an object of the present invention to provide a printer head, a printer head manufacturing method, and a printer capable of improving reliability.

In order to achieve the above object, a printer head according to the present invention combines a light source array in which a plurality of organic EL elements each having an organic film arranged between a pair of conductive films are arranged, and light from the light source array. A printer head including a lens array in which lens elements to be imaged are arranged, wherein hole injection is performed to inject holes supplied from the anode into a light emitting layer on a surface of the anode of the pair of conductive films. A layer is formed, and the hole injection layer contains a metal element.
The hole injection layer preferably contains 1.0 atm% or more of the metal element.
The hole injection layer imparts high conductivity using a dopant in order to efficiently transport holes to the light emitting layer. However, it is considered that due to the high conductivity due to the dopant effect, holes spread in the plane direction of the hole injection layer and are supplied to the light emitting layer, and light emission bleeding occurs. On the other hand, if the said structure is employ | adopted, it will become possible to reduce the function of the dopant in a positive hole injection layer with the plus ion of a metal element. As a result, the conductivity of the hole injection layer can be appropriately reduced, so that the current supplied from the anode can be prevented from spreading in the plane direction of the hole injection layer. Accordingly, it is possible to suppress bleeding of the organic EL element, and print quality can be improved.

The hole injection layer is preferably made of an organic material that exhibits acidity due to moisture absorption.
According to this configuration, since the anode is dissolved by moisture absorption of the hole injection layer, the metal element contained in the anode can be diffused into the hole injection layer.

The hole injection layer is preferably formed by drying a coating film of PEDOT / PSS.
According to this configuration, it is possible to easily form a hole injection layer that exhibits acidity due to moisture absorption.

Moreover, it is preferable that the metal element is contained in a plurality of the organic films including the hole injection layer among the organic films from the hole injection layer to the light emitting layer.
It is considered that the emission lifetime of the organic EL device is reduced by diffusing negative ion components such as sulfate ions and sulfonate ions existing in the hole injection layer into other organic films. On the other hand, if the said structure is employ | adopted, it will become possible to suppress that the negative ion component of a positive hole injection layer migrates to another organic film with the positive ion component of a metal element. Therefore, the light emission lifetime of the organic EL element can be improved, and the reliability can be improved.

The hole injection layer contains the metal element in an amount of 1.0 atm% or more, and a part of the organic film disposed adjacent to the hole injection layer contains the metal element in an amount of 0.2 atm% or more. It is desirable that Here, a part of the organic film refers to a region from the interface between the hole injection layer and the organic film to about 20 nm inside the organic film.
According to this configuration, the migration of the negative ion component of the hole injection layer to another organic film can be suppressed by the positive ion component of the metal element. Therefore, the light emission lifetime of the organic EL element can be improved, and the reliability can be improved.

The metal element contained in the hole injection layer is preferably the same metal element as the metal element contained in the anode.
According to this configuration, the physical properties and the like of the hole injection layer are close to those of the anode, and hole transport can be performed quickly and efficiently. Therefore, the light emission characteristics in the light emitting layer are improved.

On the other hand, in the method for manufacturing a printer head according to the present invention, a light source array in which a plurality of organic EL elements each having an organic film disposed between a pair of conductive films are arranged in alignment, and light from the light source array is imaged. A method of manufacturing a printer head comprising a lens array in which lens elements are arranged, wherein a hole injection layer made of an organic material that exhibits acidity by moisture absorption is formed on the surface of the conductive film containing a metal element. And exposing the hole injection layer to an atmosphere containing at least one of moisture and oxygen.
According to this configuration, since the hole injection layer absorbs moisture and exhibits acidity, the lower anode is dissolved, and the metal element contained in the anode diffuses into the hole injection layer. As a result, it becomes possible to suppress bleeding of the organic EL element, and print quality can be improved.

In the step of exposing the hole injection layer, the hole injection layer is preferably exposed to the atmosphere for 6 hours or more.
According to this configuration, since the hole injection layer sufficiently absorbs moisture, it becomes possible to suppress bleeding of light emission, and print quality can be improved.

Further, it is desirable that the step of exposing the hole injection layer is performed in an air conditioned room where the water concentration and / or oxygen concentration can be adjusted in the range of 10% to 100%, respectively.
According to this configuration, the exposure time of the hole injection layer can be shortened by adjusting the moisture concentration and / or the oxygen concentration.

Further, it is desirable that after the step of exposing the hole injection layer, a step of forming the organic film on the surface of the hole injection layer and a step of heat-treating the organic film are provided.
According to this configuration, the metal element can be diffused into a part of the organic film disposed adjacent to the hole injection layer, and the light emission lifetime can be further improved. Here, a part of the organic film refers to a region from the interface between the hole injection layer and the organic film to about 20 nm inside the organic film.

In another method of manufacturing a printer head according to the present invention, a light source array in which a plurality of organic EL elements each having an organic film disposed between a pair of conductive films is arranged and light from the light source array is coupled. A method of manufacturing a printer head including a lens array in which lens elements to be imaged are arranged, wherein a liquid material in which a metal element is dispersed in advance is applied to the surface of the conductive film, and a hole injection layer is formed. It has the process of forming, It is characterized by the above-mentioned.
Also with this configuration, a hole injection layer containing a metal element can be formed.

On the other hand, a printer according to the present invention includes the above-described printer head as an exposure unit.
According to this configuration, it is possible to provide a printer having excellent print quality and reliability.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing referred to below, the dimensions and the like of each component are appropriately changed and displayed for easy understanding.

(Printer head)
First, the printer head will be described.
FIG. 1 is a perspective sectional view of a printer head according to an embodiment. The printer head 101 includes a light source array (organic EL device) 1 in which a plurality of organic EL elements are arranged and arranged, and a lens array 31 in which lens elements that image light from the light source array 1 in an erecting equal magnification are arranged and arranged. The head case 52 that supports the outer peripheral portions of the light source array 1 and the lens array 31 is provided.

(Light source array)
FIG. 2 is a diagram schematically showing the light source array. The light source array 1 includes a light emitting element array 3A in which a plurality of organic EL (electroluminescence) elements 3 are arranged on a long and thin rectangular element substrate 2, and a driving element 4 for driving the organic EL elements 3. A drive element group and a control circuit group 4a for controlling driving of these drive elements 4 (drive element group) are integrally formed. In FIG. 2, the organic EL elements 3 are arranged in one row, but may be arranged in two rows in a staggered manner. In this case, the pitch of the organic EL elements 3 in the longitudinal direction of the light source array 1 can be reduced, and the resolution of the printer can be improved.

  The organic EL element 3 includes at least an organic light emitting layer between a pair of electrodes, and emits light by supplying a current from the pair of electrodes to the light emitting layer. A power line 8 is connected to one electrode of the organic EL element 3, and a power line 7 is connected to the other electrode via a drive element 4. The drive element 4 is composed of a switching element such as a thin film transistor (TFT) or a thin film diode (TFD). When a TFT is employed as the drive element 4, the power supply line 7 is connected to the source region, and the control circuit group 4a is connected to the gate electrode. The operation of the drive element 4 is controlled by the control circuit group 4a, and the energization to the organic EL element 3 is controlled by the drive element 4. The detailed structure and manufacturing method of the organic EL element 3 and the driving element 4 will be described later.

(Lens array)
FIG. 3 is a perspective view of the lens array. The lens array 31 is an array of SELFOC (registered trademark) lens elements 31a manufactured by Nippon Sheet Glass Co., Ltd. The lens element 31a is formed in a fiber shape having a diameter of about 0.28 mm. The lens elements 31a are arranged in a staggered manner, and a black silicone resin 32 is filled in the gaps between the lens elements 31a. Further, a frame 34 is arranged around the lens array 31 to form a lens array 31.

  This lens element 31a has a parabolic refractive index distribution from the center to the periphery. Therefore, the light incident on the lens element 31a travels while meandering inside the lens element 31a at a constant period. By adjusting the length of the lens element 31a, an image can be formed in an erecting equal magnification. In addition, according to the lens for erecting equal magnification, it is possible to superimpose images formed by adjacent lenses, and a wide range of images can be obtained. Therefore, the lens array of FIG. 3 can accurately form light from the entire light source array.

(Head case)
Returning to FIG. 1, the printer head 101 of this embodiment includes a head case 52 that supports the outer peripheral portions of the light source array 1 and the lens array 31. The head case 52 is formed in a slit shape by a rigid material such as Al. The cross section perpendicular to the longitudinal direction of the head case 52 has a shape in which both upper and lower ends are opened. The upper half side walls 52a and 52a are arranged substantially in parallel, and the lower half side walls 52b and 52b are arranged inclined toward the lower end central part.

And the light source array 1 is arrange | positioned so that the opening part formed in the upper side of the head case 52 may be plugged up. The light source array 1 is a bottom emission type, and is arranged with an element substrate, which will be described later, facing downward. In addition, sealing materials 54 a and 54 b are disposed over the entire periphery at the corner formed by the side wall 52 a of the head case 52 and the light source array 1.
On the other hand, the lens array 31 is disposed so as to close the slit-shaped opening formed on the lower side of the head case 52. Sealing materials 55a and 55b are disposed at the corner formed by the side wall 52b of the head case 52 and the lens array 31 over the entire circumference.

(Organic EL device according to the first embodiment)
Next, the organic EL device constituting the light source array described above will be described.
FIG. 4 is a side sectional view of the organic EL device according to the first embodiment. In the organic EL device 1 according to the first embodiment, a metal element is contained in the hole injection layer 70 and the part 60 of the light emitting layer.

  In general, the organic EL device 1 includes an element substrate 2, a drive circuit unit 5 disposed on the surface of the element substrate 2, a plurality of organic EL elements 3 disposed on the surface of the drive circuit unit 5, and an organic EL element. 3 is mainly composed of a sealing substrate 30 for sealing 3. The organic EL element 3 is formed in a substantially circular shape when viewed from a direction perpendicular to the element substrate 2. In the present embodiment, a bottom emission type organic EL device 1 that extracts emitted light from the organic EL element 3 from the element substrate 2 side will be described as an example.

  In the bottom emission type organic EL device 1, light emitted from the light emitting layer 60 is taken out from the element substrate 2, so that the element substrate 2 is transparent or semitransparent. For example, glass, quartz, resin (plastic, plastic film) or the like can be used, and a glass substrate is particularly preferably used.

  On the element substrate 2, a drive circuit unit 5 including a drive TFT 123 (drive element 4) of the organic EL element 3 is formed. Note that an organic EL device can be configured by mounting an IC chip having a drive circuit on the element substrate 2.

As a specific configuration of the drive circuit unit 5, a base protective layer 281 made of an insulating material is formed on the surface of the element substrate 2, and a silicon layer 241 that is a semiconductor material is formed thereon. A gate insulating layer 282 mainly composed of SiO ₂ and / or SiN is formed on the surface of the silicon layer 241. A gate electrode 242 is formed on the surface of the gate insulating layer 282. The gate electrode 242 is constituted by a part of a scanning line (not shown). Of the silicon layer 241, a region facing the gate electrode 242 with the gate insulating layer 282 interposed therebetween is a channel region 241a. On the other hand, a first interlayer insulating layer 283 mainly composed of SiO ₂ is formed on the surfaces of the gate electrode 242 and the gate insulating layer 282.

  Further, in the silicon layer 241, a low concentration source region 241b and a high concentration source region 241S are provided on one side of the channel region 241a, and a low concentration drain region 241c and a high concentration drain region 241D are provided on the other side of the channel region 241a. A so-called LDD (Lightly Doped Drain) structure is provided. Among these, the high-concentration source region 241S is connected to the source electrode 243 through a contact hole 243a penetrating the gate insulating layer 282 and the first interlayer insulating layer 283. The source electrode 243 is configured by a part of a power supply line (not shown). On the other hand, the high concentration drain region 241D is connected to a drain electrode 244 disposed in the same layer as the source electrode 243 through a contact hole 244a that penetrates the gate insulating layer 282 and the first interlayer insulating layer 283.

  Over the source electrode 243 and the drain electrode 244 and the first interlayer insulating layer 283 described above, a planarizing film 284 mainly composed of a heat-resistant insulating resin material such as acrylic or polyimide is formed. The planarizing film 284 is formed to eliminate surface irregularities due to the driving TFT 123 (driving element 4), the source electrode 243, the drain electrode 244, and the like.

  A plurality of pixel electrodes 23 are arranged in the formation region of the organic EL element 3 on the surface of the planarizing film 284. The pixel electrode 23 is connected to the drain electrode 244 through a contact hole 23 a provided in the planarizing film 284. That is, the pixel electrode 23 is connected to the high concentration drain region 241D of the silicon layer 241 through the drain electrode 244.

In addition, an inorganic partition wall 25 made of an inorganic insulating material such as SiO ₂ is formed so as to surround the pixel electrode 23 on the surface of the planarizing film 284. A plurality of functional films are laminated on the surface of the pixel electrode 23 exposed from the opening of the inorganic partition wall 25 to constitute the organic EL element 3. The organic EL element 3 of the present embodiment includes a pixel electrode 23 that functions as an anode, a hole injection layer 70 that injects / transports holes from the pixel electrode 23, a light-emitting layer 60 that is made of an organic EL material, a cathode A common electrode functioning as 50 is laminated.

In the case of the bottom emission type organic EL device 1, the pixel electrode 23 that functions as an anode is formed of a transparent conductive material. As the transparent conductive material, ITO (indium tin oxide), IZO (registered trademark, indium zinc oxide), or the like can be used. Among them, ITO is composed of a material in which indium oxide (In ₂ O ₃ ) is doped with tin (Sn).

Further, as the material for forming the hole injection layer 70, a material that exhibits acidity (preferably pH 4 or less) by moisture absorption is employed. In particular, a dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is preferably used. This PEDOT / PSS is obtained by dispersing 3,4-polyethylenedioxythiophene, which is a polythiophene derivative, in polystyrene sulfonic acid as a dispersion medium and further dispersing it in water.
The material for forming the hole injection layer 70 is not limited to those described above, and various materials can be used. For example, a material obtained by dispersing polystyrene, polypyrrole, polyaniline, polyacetylene or a derivative thereof in an appropriate dispersion medium such as the above-described polystyrene sulfonic acid can be used.

  A hole transport layer may be provided on the surface of the hole injection layer 70. The hole transport layer has a function of efficiently transporting holes supplied from the hole injection layer 70 to the light emitting layer. As a constituent material of the hole transport layer 65, a polymer compound TFB (poly (2,7- (9,9-di-n-octylfluorene) -alt- (1,4 It is desirable to employ -phenylene-((4-sec-butylphenyl) imino-1,4-phenylene)))). The molecular structure of TFB is shown in Chemical Formula 1. TFB is preferable because it is formed between the hole injection layer 70 and the light emitting layer 60 and has a role of assisting transport of holes from the hole injection layer 70 to the light emitting layer 60. In addition, the thickness of the hole transport layer 65 is formed to 20 nm or less.

  An electron blocking layer may be provided on the surface of the hole injection layer 70. The electron blocking layer has a function of preventing light supplied from the cathode from passing through the light emitting layer 60, promoting recombination of electrons and holes in the light emitting layer 60, and improving light emission efficiency. . The constituent material of the electron block layer is the same as that of the hole transport layer 65, but a material having a relatively high function of transporting holes is adopted for the hole transport layer, and the electron block layer is relatively composed of electrons. It is desirable to use a material having a high function of suppressing movement.

  On the other hand, as a material for forming the light emitting layer 60, a known light emitting material capable of emitting fluorescence or phosphorescence is used. Specifically, (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinyl carbazole (PVK), polythiophene derivative, polymethyl Polysilanes such as phenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as.

  In the present embodiment, a light emitting layer whose emission wavelength band corresponds to red is adopted, but a light emission layer whose emission wavelength band corresponds to green or blue may be adopted. As a material for forming the red organic EL layer 60, for example, MEHPPV (poly (3-methoxy 6- (3-ethylhexyl) paraphenylenevinylene) is used. As a material for forming the green organic EL layer 60, for example, polydioctylfluorene and F8BT ( For example, polydioctylfluorene may be used as a material for forming the blue organic EL layer 60 in the mixed solution of dioctylfluorene and benzothiadiazole). The thickness is not limited, and a preferable film thickness is adjusted for each color.

  The cathode 50 preferably has a laminated structure of a main cathode and an auxiliary cathode. As the main cathode, it is desirable to employ a material such as Ca, Mg, LiF having a work function of 3.0 eV or less. Thereby, since the function as an electron injection layer is provided to the main cathode, the light emitting layer can emit light at a low voltage. The auxiliary cathode has functions of enhancing the conductivity of the entire cathode 50 and protecting the main cathode from oxygen and moisture. Therefore, it is desirable to employ a metal material such as Al, Au, or Ag having excellent conductivity as the auxiliary cathode.

On the other hand, the sealing substrate 30 is bonded to the upper side of the cathode 50 via the adhesive layer 40. A sealing cap that covers the entire cathode 50 may be fixed to the periphery of the element substrate 2, and a getter agent that absorbs moisture, oxygen, or the like may be disposed inside the sealing cap. Further, an inorganic sealing film made of SiO ₂ or the like may be laminated on the surface of the cathode 50.

  In the organic EL device 1 described above, the image signal supplied from the source electrode 243 of the drive circuit unit 5 is applied to the pixel electrode 23 by the drive element 4 at a predetermined timing. Then, the holes injected from the pixel electrode 23 and the electrons injected from the cathode 50 are recombined in the light emitting layer 60 and light having a predetermined wavelength is emitted. The emitted light passes through the pixel electrode 23 made of a transparent material, the drive circuit unit 5 and the element substrate 2 and is extracted outside. Since the inorganic partition wall 25 is made of an insulating material, a current flows only inside the opening of the inorganic partition wall 25 and the light emitting layer 60 emits light. Therefore, the inside of the opening of the inorganic partition wall 25 is a pixel region of the organic EL element 3.

(Metal element)
FIG. 7A is a schematic cross-sectional view of the organic EL element according to this embodiment. The pixel electrode 23 of the organic EL element is made of a material containing a metal element. That is, since the pixel electrode 23 is made of ITO (indium tin oxide; In ₂ O ₃ doped with Sn or the like), the pixel electrode 23 contains a metal element such as In or Sn.

  On the other hand, among the organic films from the hole injection layer 70 adjacent to the pixel electrode 23 to the light emitting layer 60, a plurality of organic films including the hole injection layer 70 contain a metal element. In the present embodiment, a metal element is contained in part of the hole injection layer 70 and the light emitting layer 60. Here, a part of the light emitting layer 60 refers to a region from the interface between the hole injection layer 70 and the light emitting layer 60 to the inside of the light emitting layer 60 of about 20 nm. When the hole transport layer or the electron block layer is formed, a metal element may be contained in the hole transport layer or the electron block layer in addition to the hole injection layer 70. As this metal element, the same kind of metal element as the metal element contained in the pixel electrode 23 is contained. In the present embodiment, since the pixel electrode 23 is made of ITO, a metal element such as In or Sn is present in an ion state in the hole injection layer 70 and the light emitting layer 60.

(Method for manufacturing organic EL device)
Next, a method for manufacturing the organic EL device according to this embodiment will be described.
5 and 6 are process diagrams of the method for manufacturing the organic EL device according to the first embodiment. In FIGS. 5 and 6, for ease of understanding, the element substrate, the drive circuit unit, and the sealing substrate are not shown, and an enlarged view of part A in FIG. 6 is shown.
First, as shown in FIG. 5A, an inorganic partition wall 25 is formed around the pixel electrode 23. Next, ultrasonic cleaning of the substrate surface is performed using ultrapure water. Further, as the lyophilic process on the surface of the pixel electrode 23, an atmospheric pressure plasma process using oxygen gas or the like is performed.

  Next, as shown in FIG. 5B, a hole injection layer 70 is formed on the entire surface of the pixel electrode 23 and the inorganic partition wall 25 by a liquid phase process. Specifically, first, a liquid material for forming the hole injection layer 70 is applied to the entire substrate by spin coating, spray coating, dipping, or the like. Next, the coating film is heated and dried to remove moisture contained in the film. For example, heat treatment is performed at 180 ° C. for 15 minutes in the atmosphere.

Next, as shown in FIG. 5C, the hole injection layer 70 is left in an atmosphere in which at least one of moisture and oxygen is present. This leaving step is performed in the air conditioning room 10 in which the water concentration and / or the oxygen concentration can be adjusted.
The air conditioning room 10 includes a chamber 11 in which a substrate can be disposed, a moisture supply device 12 and an oxygen supply device 13 into the chamber 11, and an exhaust device 14 in the chamber 11. With the moisture supply device 12 and the oxygen supply device 13, the moisture concentration and the oxygen concentration in the chamber 11 can be adjusted in the range of 10% or more and 100% or less, respectively. Thereby, the inside of the chamber 11 can be maintained in an atmosphere in which at least one of moisture and oxygen is present.

  A substrate on which the hole injection layer 70 is formed is placed in the chamber 11 of the air conditioning room 10. Next, the inside of the chamber 11 is adjusted to the same atmosphere as the atmosphere (moisture concentration of 45% or less, oxygen concentration of about 21%), and the hole injection layer 70 is exposed to the atmosphere. As will be described later, the exposure time is desirably 6 hours or more. As a result, the hole injection layer 70 absorbs moisture and becomes acidic. The pixel electrode 23 is dissolved by the hole injection layer 70, and the metal element contained in the pixel electrode 23 diffuses into the hole injection layer 70.

Note that it is desirable to adopt a liquid phase process also when the hole transport layer is formed on the surface of the hole injection layer 70. Specifically, first, a TFB liquid material serving as a hole transport layer is applied to the entire substrate by a spin coating method, a spray coating method, a dipping method, or the like. Next, the hole transport layer is dried inside the N ₂ glove box. Specifically, the substrate is placed in the chamber of the N ₂ glove box, the inside of the chamber is replaced with N ₂ gas, and the concentration of moisture and oxygen in the chamber is reduced to 1 ppm or less. Next, the substrate is heated at 180 ° C. for 1 hour to dry the coating film, thereby forming a hole transport layer. Thereafter, it is desirable to remove the soluble layer of TFB with a xylene solvent. Thereby, a TFB layer insoluble in the xylene solvent is formed.
Further, when an electron blocking layer is formed on the surface of the hole injection layer 70, it can be performed in the same manner as the hole transport layer. For example, the electron block layer is formed by performing heat treatment at 200 ° C. for 15 minutes in the chamber of the N ₂ glove box.

Next, as shown in FIG. 6A, a light emitting layer 60 is formed on the surface of the hole injection layer 70 by a liquid phase process. Specifically, the liquid material for forming the light emitting layer 60 is applied to the entire substrate by spin coating, spray coating, dipping, or the like.
Next, as shown in FIG. 6B, the light emitting layer 60 is dried. This drying step is performed inside the N ₂ glove box 15. The N ₂ glove box 15 includes a chamber 16 in which a substrate can be disposed, an N ₂ gas supply device 17 into the chamber 16, an exhaust device 18 in the chamber 16, and a substrate heating device 19. Yes. The N ₂ gas supply device 17 can replace the air in the chamber with N ₂ gas.

In the chamber 16 of the N ₂ glove box 15, a substrate coated with a light emitting layer forming material is disposed. Next, the inside of the chamber 16 is replaced with N ₂ gas, and the concentration of moisture and oxygen in the chamber 16 is reduced to 1 ppm or less. Next, the substrate is heated by the heating device 19 to dry the coating film. For example, heat treatment is performed at 160 ° C. for 30 minutes. Thereby, the light emitting layer 60 is formed.
As described above, the metal element constituting the pixel electrode 23 is diffused inside the hole injection layer 70. The metal element diffuses from the hole injection layer 70 to a part of the light emitting layer 60 as the light emitting layer 60 is heated.

Next, as shown in FIG. 6C, the cathode 50 is formed by a vacuum deposition method or the like.
Thus, the organic EL device according to the first embodiment is formed.

In the organic EL device according to the first embodiment, it has been confirmed that emission of light outside the pixel region of the organic EL element (so-called emission blur) can be suppressed by including a metal element in the hole injection layer. . This is presumed to be due to the following reason.
FIG. 7B is a chemical formula of polystyrene sulfonic acid (PSS) contained in the hole injection layer and functioning as a dopant. Polystyrene sulfonic acid is negatively charged due to the presence of a sulfonic group (—SO ₃ —). As shown in FIG. 7A, positive ions of metal elements such as In + and Sn + are present in the hole injection layer containing PSS- in this embodiment. As a result, the hole injection layer 70 is considered to have a reduced dopant function and an increased electrical resistance.

  FIG. 8 is a graph showing the relationship between the exposure time to the atmosphere in the manufacturing process of the hole injection layer, the metal ion content and the current value in the hole injection layer. As the exposure time becomes longer, moisture absorption in the hole injection layer and dissolution of the pixel electrode proceed, and the metal ion content in the hole injection layer increases. Thereby, the function of the dopant in the hole injection layer is lowered and the electric resistance is increased, and the current flowing through the hole injection layer is reduced when the same voltage is applied.

  FIG. 9A is a side sectional view for explaining the current locus in the hole injection layer, and FIG. 9B is a plan view for explaining the bleeding of light emission. In the organic EL device according to the prior art, the electric resistance of the hole injection layer 70 is low. Therefore, as shown in FIG. 9A, the holes supplied from the pixel electrode 23 circulate in the plane direction of the hole injection layer through the opening of the inorganic partition wall 25 and were injected into the light emitting layer. . As a result, as shown in FIG. 9B, so-called bleeding of light emission occurred, in which the outside of the pixel region defined by the opening of the inorganic partition wall 25 emits light.

  On the other hand, in the organic EL device according to the present invention, the electric resistance of the hole injection layer 70 is high. Therefore, as shown in FIG. 9A, the holes supplied from the pixel electrode 23 linearly progress toward the light emitting layer without going around the opening of the inorganic partition wall 25. As a result, as shown in FIG. 9B, light can be emitted in almost the same range as the pixel region, and bleeding of light emission can be prevented.

On the other hand, it has been confirmed that the lifetime of the organic EL element can be improved by including a metal element in the hole injection layer 70 and its adjacent layer. The mechanism is not clear, but is presumed to be due to the following reasons.
In the polystyrene sulfonic acid shown in FIG. 7B, a sulfonic group (—SO ₃ —) may be liberated. The sulfone group penetrates into the light emitting layer 60 from the hole injection layer 70 shown in FIG. 7A (migration). As a result, it is considered that the luminous efficiency, carrier balance, and the like of the light emitting layer 60 made of an organic material are changed to cause luminance deterioration and the light emission lifetime is shortened. On the other hand, in this embodiment, positive ions of metal elements such as In + and Sn + are also present in a part of the light emitting layer 60. With this positive ion, it becomes possible to capture the negative ion component which is to diffuse into the light emitting layer by the positive ion component of the metal element. Therefore, it is possible to suppress the luminance deterioration of the light emitting layer 60 and to improve the light emission lifetime.

  FIG. 10 is an explanatory diagram for comparison between the organic EL device (Example 1) according to the first embodiment and Comparative Example 1 thereof. FIG. 10A is a table showing the concentration of the metal element in each layer, and FIG. 10B is a graph showing the luminance deterioration of the organic EL device.

  As shown in FIG. 10A, in the organic EL device according to Example 1, the concentration of the metal element in the hole injection layer is 2.4 atm%, and the concentration of the metal element in a part of the light emitting layer is 0. 2 atm%. The part of the light emitting layer refers to a region from the interface between the hole injection layer and the light emitting layer to the inside of the light emitting layer of about 20 nm. Incidentally, when the time during which the hole injection layer is exposed to an atmosphere containing at least one of moisture and oxygen (hereinafter referred to as “exposure time”) is 6 hours, the concentration of the metal element in the hole injection layer is 1. 0 atm% or more. When the exposure time is 24 hours, the concentration of the metal element in the hole injection layer is about 2.4 atm%, and the concentration of the metal element at the interface between the light emitting layer and the hole injection layer is about 0.3 atm%. is there.

  On the other hand, in the organic EL device according to Comparative Example 1, the metal element is contained only in the hole injection layer. That is, the concentration of the metal element in the hole injection layer is 0.5 atm%, but the light emitting layer contains no metal element.

  Luminous efficiency was measured for the organic EL devices according to Example 1 and Comparative Example 1. The luminous efficiency is indicated by a current value necessary for obtaining the same luminance. In Comparative Example 1, in order to obtain the same luminance as that of Example 1, a current about 1.17 times that of Example 1 was required. Thereby, it was confirmed that the luminous efficiency of Example 1 was superior to Comparative Example 1.

  Further, with respect to the organic EL devices according to Example 1 and Comparative Example 1, the change in emission luminance with time was measured. As a result, as shown in FIG. 10 (b), it was found that the rate of decrease in emission luminance in Example 1 was slower than that in Comparative Example 1. It was confirmed that when the 10% decrease in emission luminance was defined as the lifetime, the emission lifetime of the organic EL device according to Example 1 was increased to about 1.5 times that of Comparative Example 1.

  FIG. 11 is a graph showing the relationship between the time during which the hole injection layer is left in the atmosphere (exposure) and the emission lifetime of the organic EL element. The inventor of the present application manufactured various organic EL devices by changing the exposure time of the hole injection layer. The moisture concentration in the atmosphere is 45% or less, and the oxygen concentration is about 21%. And the light emission lifetime of each organic EL apparatus was measured. In FIG. 11, the light emission lifetime when the hole injection layer is exposed for 24 hours is normalized as 1. As shown in FIG. 10, the emission lifetime when the hole injection layer is exposed for 0.5 hours is as low as about 0.7, but the emission lifetime when exposed for 6 hours or more is about 0.9 to 1.1. Converged to the range. From this result, it can be said that the exposure time of the hole injection layer is desirably 6 hours or more.

  As described in detail above, the organic EL device according to the first embodiment has a configuration in which a metal element is included in the hole injection layer. According to this configuration, even when a large current is applied to ensure the luminance of the organic EL element, the organic EL element can be prevented from bleeding. As a result, the print quality of the printer head can be improved. In the organic EL device according to the first embodiment, a metal element is included in the hole injection layer and the adjacent layer. According to this configuration, even when a large current is applied to ensure the luminance of the organic EL element, the light emission life of the organic EL element can be maintained. By ensuring the luminance of the organic EL element, it is possible to perform printing with ensuring contrast even when the printing speed of the printer head is increased. For example, if the light emission lifetime of the organic EL element is increased by 1.5 times, the printing speed of the printer head can be increased by about 20%.

  Further, in the method for manufacturing the organic EL device according to the first embodiment, a step of forming a hole injection layer made of an organic material that exhibits acidity by moisture absorption on the surface of the pixel electrode containing a metal element, and at least moisture or oxygen And a step of exposing the hole injection layer to an atmosphere where one exists. According to this configuration, since the hole injection layer absorbs moisture and exhibits acidity, the lower pixel electrode is dissolved, and the metal element contained in the anode can be diffused into the hole injection layer. At that time, it is possible to form a hole injection layer containing a metal element by using the same material as that of the prior art. That is, since it is not necessary to add a metal element in advance to the liquid that is a material for forming the hole injection layer, the film formability of the hole injection layer can be improved. Further, the dispersibility of the metal element in the hole injection layer can be improved.

(Printer)
Next, the usage pattern of the printer head of this embodiment will be described.
The printer head of this embodiment is used as an exposure device in a printer. In this case, the printer head is disposed opposite to the photosensitive drum, and is used by irradiating light from the light source array onto the photosensitive drum.

(Tandem printer)
First, a tandem printer will be described with reference to FIG.
FIG. 12 is a schematic configuration diagram of a tandem printer. An image transfer unit is disposed at the center of the printer 380. The image transfer unit mainly includes a black image transfer unit K, a cyan image transfer unit C, a magenta image transfer unit M, a yellow image transfer unit Y, and an intermediate transfer belt 390. The yellow image transfer unit Y mainly includes a photosensitive drum (image carrier) 341, a charging unit 342, the printer head 101 of the present invention, and a developing device 344.

  The photosensitive drum 341 includes a photosensitive layer as an image carrier on the outer peripheral surface thereof, and is configured to be rotatable. Around the photosensitive drum 341, a charging unit 342, the printer head 101, and a developing device 344 are sequentially arranged. The charging unit (corona charger) 342 uniformly charges the photosensitive layer of the photosensitive drum 341. The printer head 101 exposes the photosensitive drum 341 to form an electrostatic latent image on the photosensitive layer. Note that the emission energy peak wavelength of the printer head 101 and the sensitivity peak wavelength of the photosensitive drum 341 are set to substantially coincide. The developing device 344 forms a visible image by attaching toner to the electrostatic latent image on the photosensitive drum 341. The developing device 344 includes a non-magnetic one-component toner as a developer, a developing roller 355 for attaching the toner to the photosensitive drum, a supply roller 356 for supplying toner to the surface of the developing roller 355, and A blade (not shown) that regulates the film thickness of the toner adhering to the surface of the developing roller 355;

  Further, an intermediate transfer belt 390 is disposed below the photosensitive drum 341. The intermediate transfer belt 390 is stretched around a driving roller 391, a driven roller 392, and a tension roller 393, and can be circulated and moved by the driving roller 391. A primary transfer roller 345 is disposed so as to face the photosensitive drum 341 with the intermediate transfer belt 390 interposed therebetween. Then, a primary transfer bias is applied to the primary transfer roller 345 to press the intermediate transfer belt 390 against the photosensitive drum 341. As a result, the toner image formed on the photosensitive drum 341 is primarily transferred to the intermediate transfer belt 390. A cleaning unit 346 for removing residual toner on the surface of the photosensitive drum 341 is provided in the vicinity of the primary transfer position.

  Similar to the yellow image transfer unit Y described above, a magenta image transfer unit M, a cyan image transfer unit C, and a black image transfer unit K are configured and arranged along the intermediate transfer belt 390. Each color image transfer unit performs primary transfer of each color toner image to the intermediate transfer belt 390, thereby forming a full color toner image in which the respective color toner images are superimposed.

  On the other hand, below the printer 380, a paper feed cassette 363 in which a large number of recording media P are stacked and held is provided. A pickup roller 364 that feeds the recording media P one by one and a gate roller pair 365 that defines the supply timing of the recording media P are provided at the end of the paper feed cassette 363. Further, a secondary transfer roller 366 is provided to face the driven roller 392 of the intermediate transfer belt 390. Then, the recording medium P supplied onto the secondary transfer roller 366 is pressed against the intermediate transfer belt 390 on the driven roller 392. As a result, the full-color toner image formed on the intermediate transfer belt 390 is secondarily transferred to the recording medium P. A cleaning unit 367 for removing residual toner on the surface of the intermediate transfer belt 390 is provided in the vicinity of the secondary transfer position.

  Further, a fixing roller pair 361 for fixing the toner image to the recording medium P is provided on the downstream side of the secondary transfer position. On the downstream side of the fixing roller pair 361, a paper discharge roller pair 362 that discharges the recording medium P onto a paper discharge tray 368 formed on the upper portion of the printer 380 is provided. The tandem printer 380 is configured as described above.

  Since the printer 380 includes the printer head 101 of the present invention, even when a large current is applied in order to ensure the luminance of the organic EL element, it is possible to suppress bleeding of the organic EL element. In addition, the light emission lifetime of the organic EL element can be maintained. Even if the printing speed is increased, it is possible to perform printing while ensuring contrast. Therefore, it is possible to provide a printer having excellent print quality and reliability.

(4-cycle printer)
Next, a 4-cycle printer will be described.
FIG. 13 is a schematic configuration diagram of a 4-cycle printer. The printer 160 includes a charger 168, a printer head 167, and a developing device 161 having a rotary configuration around the photosensitive drum 165. The configurations of the photosensitive drum 165, the charger 168, and the printer head 167 are the same as those of the above-described tandem printer.

  The rotary developing device 161 includes a yellow developing unit Y, a cyan developing unit C, a magenta developing unit M, and a black developing unit K, and is configured to be rotatable around a central shaft 161b. Inside the yellow developing unit Y, yellow toner, a developing roller 162 for attaching the toner to the photosensitive drum 165, a supply roller 163 for supplying toner to the developing roller 162, and a toner for the developing roller 162 And a regulating blade 164 for regulating the thickness to a predetermined thickness. When a high voltage is applied to the developing roller 162, a yellow image is formed on the surface of the rotating photosensitive drum 165.

  An intermediate transfer belt 169 is disposed above the photosensitive drum 165. The intermediate transfer belt 169 is stretched between the driving roller 170a and the driven roller 170b. If the drive roller 170 a is connected to the drive motor of the photosensitive drum 165, the intermediate transfer belt 169 can be circulated and moved in synchronization with the photosensitive drum 165. If a step motor is employed as the drive motor, color misregistration correction of the intermediate transfer belt 169 can be performed. A primary transfer roller 166 is disposed so as to face the photosensitive drum 165 with the intermediate transfer belt 169 interposed therebetween. By pressing the intermediate transfer belt 169 against the photosensitive drum 165 by the primary transfer roller 166, the yellow image formed on the photosensitive drum 165 is primarily transferred to the intermediate transfer belt 169.

  On the other hand, a paper feed tray 178 for storing paper is provided below the printer 160. A pickup roller 179 that supplies paper one by one is provided at the end of the paper feed tray 178. A paper conveyance path 174 extending from the pickup roller 179 is provided with a plurality of conveyance rollers for conveying the paper. The conveying roller is driven by a low-speed brushless motor or the like. Further, a secondary transfer roller 171 is disposed so as to face the driving roller 170a with the paper conveyance path 174 interposed therebetween. The secondary transfer roller 171 can be brought into contact with and separated from the intermediate transfer belt 169 by a clutch. The sheet supplied onto the secondary transfer roller 171 is pressed against the intermediate transfer belt 169 disposed on the drive roller 170a. As a result, the yellow image formed on the intermediate transfer belt 169 is secondarily transferred to the sheet.

On the downstream side of the secondary transfer position, a fixing device for fixing the image on the sheet is disposed. The fixing device is provided with a heating roller 172 and a pressure roller 173.
A paper discharge roller pair 176 is disposed on the downstream side of the fixing device. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. When the paper discharge roller pair 176 is rotated in the reverse direction from this state, the paper traveling direction is reversed, and the paper advances in the double-sided printing conveyance path 175 in the direction of arrow G. While the sheet is waiting on the conveyance path 175, the yellow image for back side printing is primarily transferred to the intermediate transfer belt 169. Then, the paper is supplied to the secondary transfer position at an appropriate timing, and the yellow image is secondarily transferred from the intermediate transfer belt 169 to the paper.

  When the yellow image is secondarily transferred onto both sides of the paper, the rotary developing device 161 is rotated 90 degrees in the direction of arrow A, and the same processing is performed on the cyan image. Further, by performing the same processing for the magenta image and the black image, a full color image in which the respective color images are superimposed is formed on the paper. The 4-cycle printer 160 is configured as described above.

  Since this printer 160 also includes the printer head 167 of the present invention, even when a large current is applied in order to ensure the luminance of the organic EL element, it is possible to suppress bleeding of the organic EL element. In addition, the light emission lifetime of the organic EL element can be maintained. Even if the printing speed is increased, it is possible to perform printing while ensuring contrast. Therefore, it is possible to provide a printer having excellent print quality and reliability.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.

In the above embodiment, the bottom emission type organic EL device has been described as an example. However, the present invention can also be applied to a top emission type organic EL device. The pixel electrode of the top emission type organic EL device is made of a highly reflective metal material such as Al or Cr. In order to improve the hole injection property, ITO or IZO (registered trademark) is formed on the surface of the metal material. This is because a transparent conductive material such as
In the above embodiment, the organic EL device has been described as an example. However, in order to stably drive an organic semiconductor that actively uses an organic substance, the present invention can be applied to all organic semiconductors.

It is a cross-sectional perspective view of a printer head. FIG. 2 is a schematic plan view of a printer head. It is a perspective view of a lens array. 1 is a side cross-sectional view of an organic EL device according to a first embodiment. It is process drawing of the manufacturing method of the organic electroluminescent apparatus concerning 1st Embodiment. It is process drawing of the manufacturing method of the organic electroluminescent apparatus concerning 1st Embodiment. (A) is the schematic diagram of the cross section of an organic EL element, (b) is a chemical formula of polystyrene sulfonic acid. It is a graph which shows the relationship between the exposure time in air | atmosphere in the manufacturing process of a positive hole injection layer, the metal ion content rate in a positive hole injection layer, and an electric current value. FIG. 9A is a side cross-sectional view for explaining a current trajectory in the hole injection layer, and FIG. 9B is a plan view for explaining light emission bleeding. FIG. 3 is an explanatory diagram for comparison between the organic EL device according to the first embodiment (Example 1) and Comparative Example 1; It is a graph which shows the relationship between the air exposure time of a positive hole injection layer, and the lifetime of an organic EL element. 1 is a schematic configuration diagram of a tandem printer. FIG. 2 is a schematic configuration diagram of a 4-cycle printer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL apparatus (light source array) 3 ... Organic EL element 10 ... Air-conditioning chamber 23 ... Pixel electrode (anode, electrically conductive film) 25 ... Inorganic partition wall 31 ... Lens array 31a ... Lens element 50 ... Cathode 60 ... Light emitting layer 70 ... Positive Hole injection layer 101 ... Printer head

Claims (13)

A light source array in which a plurality of organic EL elements each having an organic film disposed between a pair of conductive films are arranged in alignment, and a lens array in which lens elements for imaging light from the light source array are arranged. A printer head,
A hole injection layer for injecting holes supplied from the anode into the light emitting layer is formed on the surface of the anode of the pair of conductive films,
The printer head according to claim 1, wherein the hole injection layer contains a metal element.   2. The printer head according to claim 1, wherein the hole injection layer contains 1.0 atm% or more of the metal element.   The printer head according to claim 1, wherein the hole injection layer is made of an organic material that exhibits acidity by absorbing moisture.   4. The printer head according to claim 1, wherein the hole injection layer is formed by drying a coating film of PEDOT / PSS.   5. The metal element is contained in a plurality of the organic films including the hole injection layer among the organic films from the hole injection layer to the light emitting layer. The printer head according to claim 1. The hole injection layer contains 1.0 atm% or more of the metal element,
6. The printer head according to claim 5, wherein a part of the organic film disposed adjacent to the hole injection layer contains the metal element in an amount of 0.2 atm% or more.   The printer head according to claim 1, wherein the metal element is a metal element of the same type as the metal element contained in the anode. A light source array in which a plurality of organic EL elements each having an organic film disposed between a pair of conductive films are arranged in alignment, and a lens array in which lens elements for imaging light from the light source array are arranged. A method for manufacturing a printer head, comprising:
Forming a hole injection layer made of an organic material that exhibits acidity by moisture absorption on the surface of the conductive film containing a metal element;
Exposing the hole injection layer to an atmosphere in which at least one of moisture or oxygen is present;
A method of manufacturing a printer head, comprising:   9. The method of manufacturing a printer head according to claim 8, wherein in the step of exposing the hole injection layer, the hole injection layer is exposed to the atmosphere for 6 hours or more.   The exposure process of the hole injection layer is performed in an air conditioned room in which a moisture concentration and / or an oxygen concentration can be adjusted in a range of 10% to 100%, respectively. A method for manufacturing a printer head. After the step of exposing the hole injection layer, forming the organic film on the surface of the hole injection layer;
Heat-treating the organic film;
11. The method of manufacturing a printer head according to claim 8, further comprising: A light source array in which a plurality of organic EL elements each having an organic film disposed between a pair of conductive films are arranged in alignment, and a lens array in which lens elements for imaging light from the light source array are arranged. A method for manufacturing a printer head, comprising:
A method of manufacturing a printer head, comprising: applying a liquid material in which a metal element is dispersed in advance to the surface of the conductive film to form a hole injection layer.   8. A printer comprising the printer head according to claim 1 as exposure means.

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